1. Field of the Invention
This invention relates to an in-vehicle digital broadcast reception apparatus for receiving a satellite digital broadcast and a ground digital broadcast.
2. Description of the Related Art
Hitherto, BS (Broadcasting Satellite) digital broadcasts from broadcasting satellites, CS (Communication Satellite) digital broadcasts from communication satellites, and the like have been carried out as satellite digital broadcasts using artificial satellites in geostationary orbits. Start preparation for ground digital broadcasts for conducting digital broadcasts through antennas installed on the ground is also being advanced. Association of Radio Industries and Businesses (ARIB) advances standardization work for the digital broadcasts, and the technique of ISO (International Standards Organization) 13818 called MPEG2 of color moving picture compression techniques internationally defined by MPEG (Moving Picture Experts Group) is adopted. In MPEG2, coded video and audio are put into a packet and the packet is transmitted in the TS (Transport Stream) format of a fixed length suitable for transmission.
FIG. 10 shows a configuration of an MPEG-TS signal transmitted in a digital broadcast. In the MPEG-TS signal, contents of a plurality of services and programs containing video, audio, and data can be multiplexed for transmission. The data of each service or program is divided into a plurality of TS packets. Each TS packet has a fixed length of 188 bytes and contains a four-byte packet header. The packet header contains a packet identifier (PID) to make it possible to identify the TS packet. The TS packets having the same PID provide the data of the same service or program. As special information identified by the PID of the TS packet, PSI (Program Specific Information) and SI (Service Information) are also used to facilitate selection and viewing out of a large number of types of services and programs. Further, service, called EPG (Electronic Program Guide), for providing a function for enabling the user to peruse, search, and preselect a program scheduled for broadcast is also available. Information of SI is used for the EPG. The data broadcast with the MPEG-TS signal is described using a document description language called BML (Broadcast Markup Language). The EPG can also be provided using the BML.
FIG. 11 shows an outline of a data broadcast using the BML. The description with tags as shown as BLM DOCUMENT 1 is transmitted as the data in the MPEG-TS signal as shown in FIG. 10. It is assumed that the description of BLM DOCUMENT 1 defines relationships among objects as shown as OBJECT TREE 2, for example, and specifically defines superposing of MOVING PICTURE PLANE 3, STILL PICTURE PLANE 4, and TEXT/GRAPHICS PLANE 5 to generate display screens 6a and 6b. As a moving picture displayed on the MOVING PICTURE PLANE 3, an image transmitted as video in the MPEG-TS signal can be used. In the STILL PICTURE PLANE 4, a background image and a window formed by clipping a part of the background image are transmitted as data. In the TEXT/GRAPHICS PLANE 5, data for button display of ITINERARY 5a, CHARGE 5b, and RESERVE 5c is transmitted as event elements. Any of the event elements is to be selected by the viewer and in the initial state, focus display such that ITINERARY 5a at the top is selected is produced, for example. The display screen 6a is formed by superposing MOVING PICTURE PLANE 3, STILL PICTURE PLANE 4, and TEXT/GRAPHICS PLANE 5 in order with the focus display of ITINERARY 5a. The moving picture on MOVING PICTURE PLANE 3 is scaled down to a window 4a of STILL PICTURE PLANE 4.
On the display screen 6a, the user can change event element selection by operating a remote control 7. When the viewer presses a downward arrow key 7a of the remote control 7, an event 8 of remote control key down occurs. As response operation 9, the focus moves to CHARGE 5b below ITINERARY 5a on TEXT/GRAPHICS PLANE 5, and the whole display screen 6b is displayed. When the viewer presses a DETERMINE key 7b of the remote control 7, the operation corresponding to the focus-displayed event element at the time is performed. This operation is described in BLM DOCUMENT 1. For example, when ITINERARY 5a is selected, a tour itinerary is displayed; when CHARGE 5b is selected, the tour charge is displayed. The remote control 7 is also provided with numeric keys 7c for entering a numeric value, special keys called color buttons 7d of blue, red, green, and yellow, and the like.
The data broadcast realized using the BML as shown in FIG. 11 is intended to be received at a home television receiver and it is assumed that the remote control 7 is used to operate the data broadcast. On the other hand, a digital broadcast can also be received at a mobile unit and a data broadcast can also be provided; it is expected that the broadcast will be used effectively to convey traffic information, etc. However, to operate an in-vehicle receiver, preferably a touch panel rather than a remote control is used considering safety.
A touch panel is formed on the surface of a liquid crystal display, etc. (see JP-A-Hei. 9-44307) The touch panel is, for example, a transparent resistance film and as the resistance value is lowered because of a contact pressure, the touch position is detected. To guide the operator as to which part of the touch panel is to be touched, an operation image of buttons, etc., is displayed on the display. The display with the touch panel also produces image display on the surface of in-vehicle machine for the necessity of operation. As for a touch panel using a large plasma display panel (PDP), function expansion is also proposed. (see JP-A-2000-148347)
In a digital broadcast, data described in the BML is transmitted assuming that the user operates the remote control 7, as described above. However, with an in-vehicle machine having the remote control 7, an operation fitted for a data broadcast cannot be performed, and data cannot be used effectively.